This invention relates to overfill valves for storage containers and in particular, to devices capable of retrofitting such containers insitu. While the invention is described with particular reference to its use in storage containers in filling stations or gasoline station environments, those skilled in the art will recognize the wider applicability of the inventive principals disclosed hereinafter.
Liquid storage containers such as in-ground tanks are often used to store highly toxic or flammable fluids and chemicals. The gasoline storage tanks used at filling or service stations to hold the various gasolines and diesel fuels sold to customers are a common example of the type of tank or container with which the present invention finds application. Access to such in-ground tanks for purposes of measuring the fluid contained therein, and for adding such fluid commonly is through a fill pipe. The fill pipe normally is closed or sealed at ground level by a cover that is removed for filling operations. At such times, a hose is inserted into the fill pipe and the fluid is pumped into the container through the hose.
A recurring problem with storage tanks is spillage of fluid. Spillage often occurs as a result of tank overflow and creates a potentially hazardous situation given the volatile and dangerous nature of gasoline, for example. Notwithstanding the potentially hazardous situation, evaporation of gasoline in the atmosphere is an environmentally undesirable situation. Various governmental regulations have been imposed requiring owners of the containers and the people who service or fill them to take precautions against spillage. As a consequence, several approaches have been developed in the prior art to prevent such spillage. Monitoring systems, for example, are available which automatically sense the level of fluid in the tank and shut the filling or pumping system down when the monitoring system senses that the tank is at or near full capacity.
A second approach has been to use overfill valves which can be retrofitted to the storage container. Overfill valves have the advantage of being cheaper than available monitoring systems. However, the valves must meet certain requirements if they are to find wide application. Commonly, the storage level of gasoline tanks is determined from dip sticks which are manually placed into the tanks and read. Consequently, overflow valves must be sufficiently non-restrictive to permit insertion and removal of the manual measuring instrument. The valves also must be relatively easy to be placed in operation, must not contaminate the fluid being stored and must be capable of easy removal if the valve malfunctions in operational use.
A number of prior art devices have been developed in an attempt to meet these requirements. These include the constructions shown in United States Patent to Draft, No. U.S. Pat. No. 4,667,711, the United States Patent to McGillis, No. U.S. Pat. No. 3,963,041, and the United States Patent to McGillis et al, No. U.S. Pat. No. 3,078,867, as well as the French Patent to Robyn, No. U.S. Pat. No. 1,360,869. While the prior art constructions described in the above referenced patents work to perform their intended functions, they are not without drawbacks. For example, additional openings sometimes must be made in the tank in order to install the device. The valve assemblies themselves often are complicated and malfunction in applicational use. The installation of valve assemblies into pre-existing fill pipes requires that the assembly conform to an envelope which is less than the diameter of the fill pipe in which the assembly is placed. While certain constructions of the prior art do provide for such insertion, their designs are such that installation is not readily accomplished. In some designs, it is necessary to have an opening in the side of the valve. A float mechanism for operating the valve head fits in this opening and nests within the opening when so positioned. Openings in the pipe are not acceptable in gasoline storage facilities. In gasoline storage tanks, discharge of liquids into the tank must occur at or near the bottom of the storage tank. Openings in the valve to permit its installation do not satisfy this discharge requirement.
We are aware of other designs which close such opening by various means. Sometimes complicated closure structures are provided. In other designs, the shell is formed to correspond to a specially designed float construction. In these constructions, the float is designed to conform to the required envelope for insertion without using an opening in the valve. Special float designs are expensive and the materials from which the floats themselves are constructed often contaminate the fluids being stored in the tank. In addition, some assemblies use complex valve designs or designs so the valve head can be placed at only one location within the valve structure. The complexity of the construction requires specially designed valve seats which adds to the cost of the assembly, while attaching the valve head at a single position in the assembly limits the design flexibility and may require a precise seating arrangement to ensure proper closure of the valve.
It is an object of the present invention to provide an overflow valve apparatus which is useful in containers such as in-ground storage tanks that hold dangerous, toxic or flammable liquids to facilitate filling the tank while, at the same time, preventing overfilling of the tank and the potentially hazardous spills resulting therefrom.
Another object of this invention is to provide such an apparatus having a float mechanism external to a fill tube of the assembly but which readily conforms to an envelope defined by the diameter of the fill tube so that the apparatus can be readily installed and removed in a fill pipe of an associated storage tank.
Another object of this invention is to provide valve apparatus in which a float mechanism may be accommodated in the envelope of the fill tube during installation and removal, the float mechanism being positioned externally of the fill tube at all times.
Yet another object of this invention is to provide an overflow valve apparatus which is low in cost, simple in design, and which does not require a special seating structure therein to close off fluid flow through it.
A further object of this invention is to provide an overflow valve apparatus in which fluid flow through the valve is directed away from the valve head so as to not inadvertently close the valve head prior to the container being substantially full but which aids the seating of the valve head as the container becomes substantially full.
A still further object of this invention is to provide such an apparatus having a drain mechanism by which fluid in the fill tube when the valve closes can readily drain into the container.
Another object of this invention is to provide such an apparatus constructed from materials which do not contaminate the fluid with which the container is filled.
Yet another object of this invention is to provide a simplified spring arrangement for biasing a float mechanism to an operative position.
Still another object of this invention is to provide an overfill valve apparatus which is installable insitu without alteration to an in-place container.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.